This invention relates to dispensing volatile materials such as pest control materials, including but not limited to insecticides and insect repellents, and fragrances. More particularly, it relates to volatile material-containing mats that are employed in conjunction with electrical, gas, flammable liquid, or wax-fueled heaters or other sources of heat. One type of electrical heater used for this purpose is sold by S.C. Johnson & Son, Inc. under the trademark FUYI VAPE.TM..
It is known in the art to impregnate a solid, porous cellulosic mat with a volatile material or to place a volatile material in a pan-like metal structure. These mats and pans are placed on heaters to cause the volatile material to vaporize into the atmosphere.
A problem with the metal pan-like structures is that for typical heaters they can cause a volatile material to be exposed to too much heat. This can cause the volatile to be used up too fast or be deteriorated or destroyed through thermal degradation.
The mats have similar problems and also have problems with respect to their being exposed to differing temperatures across a heater surface. Low-cost existing heaters often have hotter regions at certain points along their burner surface. The mats therefore can have uneven and inefficient vaporization.
The above problems are of increased concern for extended longevity products intended to be used for a week or more. Merely adding additional volatile to increase product capacity and longevity does not work well because prolonged exposure of volatiles to too high temperatures can degrade or destroy the volatile and because, with hot temperatures, a disproportionate amount of the volatile can be driven off initially, with an insufficient amount surviving to be released in useful amounts at a later time.
Another design consideration is that existing heaters, for safety and other reasons, often only accept slab-like inserts having a small cross-sectional shape, necessary to fit into a small heater loading port or opening. Thus, any solution to the extended longevity problem preferably takes into account size restrictions imposed by existing heaters.
Yet another critical design consideration is cost. Mats of this type are often used in countries that have very modest average annual incomes. To have much practical application in those countries, the mats must be inexpensive.
As such, it can be seen that a need exists for an improved volatile dispensing device.